1. Field of the Invention
The present invention relates to a walking assistance system that assists walking by permitting a user's upper leg swing in the fore-and-aft direction around a hip joint by means of a hip joint actuator and permits a user's lower leg swing in the fore-and-aft direction around a knee joint by means of a knee joint actuator.
The present invention also relates to a walking assistance system that assists walking by permitting a user's lower leg swing in the fore-and-aft direction around a knee joint by means of a knee joint actuator.
2. Description of the Related Art
Japanese Patent Application Laid-open No. 2002-301124 discloses a walking assistance system that assists the movement of a user's upper leg by connecting, via an electric actuator positioned on the outside of the hip joint, a first link fixed to a side face of an abdominal belt wrapped around the user's abdomen and a second link fixed to side faces of upper leg supports wrapped around the user's upper leg, and by making the second link swing in the fore-and-aft direction relative to the first link by means of the electric actuator.
In the walking assistance system having this structure, the upper end of the second link, which is positioned along the user's upper leg, is pivotably supported so that it can swing relative to the hip, and a lower end part thereof is fixed by means of the upper leg supports so that it is unable to move relative to the upper leg.
FIG. 21 of the drawings is a schematic diagram in which the user's upper right leg, equipped with the walking assistance system, is viewed from the front, wherein a point A denotes a pivoting support point of the upper end of the second link of the walking assistance system, a point B denotes a point at which the lower end of the second link is fixed to the upper leg, a point C denotes the user's knee joint, and a point D denotes the user's hip joint. Considering a rectangle ABCD as a four-joint link, a side AD is fixed to the user's hip, a side AB corresponds to the second link, a side CD corresponds to the thighbone, and a side BC corresponds to the upper leg supports.
When a user equipped with the walking assistance system walks, the side BC swings in a direction perpendicular to the paper surface with the point A and the point D as centers, but during this process a slight movement of the side BC in the left-and-right direction within the paper plane is inevitable. In this case, since an angle θ formed between the side AB (the second link 20) and the side BC (the upper leg supports 15f and 15r) is fixed, in order for the side BC to move in the left-and-right direction within the paper plane, it is necessary for slippage to occur at the point C. That is, the upper leg supports, which are wrapped around the user's upper leg, rub against the upper leg. In this way, when the upper leg supports rub against the upper leg, there is a problem that the skin of the upper leg is pulled, thus giving the user an uncomfortable sensation.
In the walking assistance system disclosed in Japanese Patent Application Laid-open No. 2002-301124, the second link can swing only in the fore-and-aft direction relative to the first link around a left-and-right direction axis, and the user's upper leg can therefore swing only in the fore-and-aft direction.
However, during walking, the upper leg not only swings in the fore-and-aft direction but also swings in the left-and-right direction to a slight extent. Since the above-mentioned conventional arrangement does not have the degree of freedom to allow the upper leg to swing in the left-and-right direction, the user might feel uncomfortable while walking. In order to avoid this, the second link, which is positioned along the upper leg, may be formed from a soft material having flexibility and made to follow the movement of the upper leg in the left-and-right direction, but unless the framework of the walking assistance system including the second link is made to have a certain rigidity, the weight of the walking assistance system itself cannot be let through to the ground, and the weight is imposed on the user, thus putting a large burden on the user.
FIG. 22 of the drawings is a schematic diagram of a knee joint of a human body; reference numeral 01 denotes a thighbone, and reference numeral 02 denotes a shin bone. The upper end of the shin bone 02 is substantially flat, and the lower end of the thighbone 01, which abuts against the shin bone 02, is curved in an arc shape. When, for example, the knee joint is bent in order to sit on a chair, the thighbone 01 swings rearward through 90° relative to the shin bone 02. It is known that during a first stage of the swing the lower end of the thighbone 01 is mainly in rolling contact with the upper end of the shin bone 02, and during a second stage of the swing the lower end of the thighbone 01 is mainly in sliding contact with the upper end of the shin bone 02. Therefore, due to the rolling contact between the shin bone 02 and the thighbone 01 accompanying bending of the knee joint, a lower part of the thighbone moves rearwardly relative to the shin bone 02 by a distance X. Similarly, when, for example, the knee joint is bent in order to kick a lower part of the knee rearwardly, an upper part of the shin bone 02 moves rearwardly relative to the thighbone 01 by a distance X as shown in FIG. 23 of the drawings.
In this way, since in the conventional walking assistance system the upper leg fitting and the lower leg fitting are pivotably supported via the simple pin coupling in spite of the knee joint moving uniquely and in a different manner from a simple pin coupling, the upper leg fitting and the lower leg fitting cannot follow the movement of the knee joint, leading to problem that they rub against the user's skin to provide an uncomfortable sensation.